In recent years, there have been proposed and developed various lane deviation avoidance systems for adaptive cruise control (ACC) system equipped vehicles. One way to prevent or avoid lane deviation of such an ACC vehicle is to actively apply braking forces to road wheels in such a manner that a yawing moment acts on the vehicle in the direction that lane deviation is prevented. One such lane deviation avoidance system has been disclosed in Japanese Patent Provisional Publication No. 2000-33860 (hereinafter is referred to as “JP2000-33860”). The lane deviation avoidance system has a controller that executes lane deviation avoidance control so that braking forces are applied to respective road wheels on the opposite side to the direction of lane deviation, when the ACC vehicle is apt to deviate from the driving lane.